Producing petroleum from a subsurface formation



Feb. 4, 1964 J. C. ALLEN PRODUCING PETROLEUM FROM A SUBSURFACE FORMATION Filed July 2, 1958 arma/7a ,/2

United States Patent O 3,i2i),265 PRODUCENG lEl-.LEUM FROM A SUBSURFAQE FORMAHOH Joseph C. Allen, Bellaire, Tern, assigner to Texaco inc., a corporation of Beiaware File duly 2, H53, Ser. No. 746,234 2 Clmrns. (Cl. lee-42) This invention relates to the recovery and production of petroleum from a subsurface petroleum-producing formation. In accordance with one embodiment this invention relates to the recovery and production of petroleum from a subsurface petroleum-containing formation employing an operation wherein a well bore is employed both as a gas injection well and as a petroleum production well.

One of the most efficient methods of displacing petroleum from a subsurface petroleum-producing formation, particularly a formation having considerable structural relief, is the injection of gas high in the formation, near the top or crest, and producing oil from near the bottom of the formation or lower portion thereof. By operating in this fashion advantage is taken of the natural segregating effect of gravity. There are many formations, however, which possess relatively little structural relief or dip. In the production of petroleum from such formations by injection of gas into the upper portion thereof a multitude of injection wells is required so that the injected gas is forced evenly downwardly, in a blanket-like manner, into the petroleum-producing formation while producing petroleum from the lower portions thereof so that during the gas injection and petroleum production operations advantage may be taken of the segregating effect of gravity. As indicated, however, this method involves the employment of very many wells and, consequently, in most instances is economically prohibitive.

lt is an object of this invention to provide an improved method for the recovery and production of petroleum from a subsurface petroleum-producing formation.

Another object of this invention is to provide an improved method of recovering and producing petroleum from a subsurface petroleum-producing formation involving operations wherein the same well bore penetrating the petroleum-producing formation is employed as a gas injection well and as a petroleum production well.

Another object of this invention is to provide a method wherein a petroleum-producing formation can be produced by the injection of gas into the upper portion thereof while petroleum is being produced from the lower portion thereof, and wherein premature lingering or short circuiting of the injected gas from the upper portion of the formation into the lower portion of the formation in the vicinity of the well bore during the petroleum production operation is inhibited or obviated.

Yet another object of this invention is to provide a method for the production of petroleum from subsurface petroleum-producing formations having relatively little structural relief or dip.

Still another object of this invention is to provide a method of producing petroleum from subsurface petroleum-producing formations involving operations wherein advantage is taken of the segregating effect of gravity,

How these and other objects of this invention are accomplished will become apparent in the light of the accompanying disclosure and drawing wherein there is schematically illustrated a petroleum production operation carried out in accordance with the practice of this invention. In at least one embodiment of the practice of this invention at least one of the foregoing objects will be achieved.

In accordance with this invention an improved method of recovering and producing petroleum from a subsurface petroleum-containing formation is accomplished by creating a water block, i.e., a water permeable, substantially gas or hydrocarbon impermeable zone, in the upper portion of the petroleum-producing formation in the vicinity of the Well bore, followed by the injection of gas into the upper portion of the formation at a location above the aforesaid gas or hydrocarbon impermeable Zone and producing petroleum from the lower portion of the formation beneath the aforesaid gas or hydrocarbon impermeable zone. A

Various methods may be employed in the practice of this invention for the creation of a water permeable and gas or hydrocarbon impermeable zone in the upper portion of the formation prior to the injection of gas into the formation above said zone. One method particularly suitable for use in the practice of this invention involves fracturing the petroleum-producing formation in the upper portion thereof to create a substantially horizontal fracture, such as a fracture extending substantially horizontally, radially outwardly from the well bore. The resulting fracture is then treated by the injection of water or aqueous solution thereinto to form a water block therein and within the immediately surrounding formation with the result that the fracture and that portion of the formation inmediately encompassing the fracture are rendered substantially gas or hydrocarbon impermeable. Desirably in accordnace with one embodiment of the practice of this invention the petroleum-producing formation is fractured in the upper portion thereof by employing as the fracturing fluid an aqueous liquid such as water, brine or an aqueous oil suspension, such as a suspension of oil in water. When a fracturing operation is carried out while employing an aqueous fracturing uid the fracture and water block encompassing the fracture are created substantially at the same time with the result that after the fracturing operation is completed the fracture and that portion of the formation encompassing the fracture are rendered substantially gas or hydrocarbon (oil) impermeable. Other methods of creating a substantially gas or hydrocarbon impermeable water block or similar removable barrier within a petroleum-producing formation are known.

Any gas may be suitably employed as a pressuring gas in the practice of this invention. Desirably, however, the gas injected into the petroleum-producing formation, above the fluid or gas impermeable Zone created therein, is natural gas, preferably gas recovered from the formation undergoing treatment. Natural gas comprises a major amount of methane and minor amounts of ethane, propane and butane. Accordingly, any of the aforesaid normally gaseous hydrocarbons, alone or in any suitable admixture, may be suitably employed in the practice of this invention as the pressuring gas. Other suitable pressuring gases include flue gas, carbon dioxide, carbon monoxide, air, nitrogen, etc.

The substantially liquid hydrocarbon and gas impermeable zone created within the upper portion of the petroleum-producing formation extends substantially horizontally, outwardly, radially from the well bore for a considerable distance, such as a distance in the range lil-260 feet, more or less. Preferably the outer periphery of the gas impermeable zone created within the upper portion of the petroleum-producing formation is suiciently removed from the well bore and the lower portion of the formation wherefrom petroleum is produced so that the buoyancy effect, exerted upon the gas injected into the upper portion of the formation, due to the density difference between the gas and the denser liquid petroleum therein, is at least as great as or greater than the pressure differential, exerted upon an increment of gas at the outer periphery of the zone, resulting from the ilow of petroleum into the well bore in the lower portion of the formation during the petroleum-producing operation. In other words, th injected gas which reaches the outer periphery of the zone will not be drawn downward directly but will occupy the upper portion of the formation and descend in blanket-like fashion to displace petroleum into the lower portion of the formation.

Referring uow'in detail to the accompanying drawing which. schematically illustrates an embodiment of the practice of this invention wherein natural gas is injected into the upper portion of the formation while petroleum is produced from the lower portion of the formation, the gas being injected into and the petroleum being produced via the same well bore, a well bore 11 is shown penetrating petroleum-producing formation 12. The well bore is provided with casing 14. In accordance with this invention, as illustrated in the drawing, a fracture extending substantially horizontally and radially outwardly from well bore 11 is created within the petroleum-producing formation 12 in the upper portion thereof. A water block, formed by the injection of water into fracture 15 and the encompassing formation, in the form of al pancake-shape water permeable, gas impermeable zone s'urroundstwell bore 11. The outline of the water block i's indicated by dashed line 17.

Y There is provided within the well bore 11, substantially concentric with respect to casing 14 therein, production tubing 16. In the annular space between production tubing 16 and casing 14, above fracture 15 and water block 17, there is positioned a packer 18 made of suitable expansible material. The packer 1S serves to make a fluid tight seal between casing 14 and production tubing 16. Following the setting of packer 18 natural gas, methane, supplied from a suitable source at the surface via conduit 19 is injected into Vthe annular space between casing 14 and tubing 16. The thus-injected gas flows down the Yannulus between casing 14 andV tubing 16 and outwardly into the upper portion of petroleum-producing formation 12 via perforations 20 at a location above fracture 15 and water block 17. As the gas is injected into the upper portion of the formation above the gas impermeable zone or water block 177,V or subsequently thereto, petroleum is produced continuously or intermittently from the lower portion of Vformation 12 via perforations 21 provided in the lower end of casing (14. The resulting produced petroleum moves upwardly within production tubing 16Yand is produced at the surface via conduit 22.

In accordance with the foregoing operations injected.

tends to follow the contour lines within the producing formation 12 and migrates in a blanket-like manner downwardly within formation 12 displacing the hydrocarbons. It is to be noted also that the gas impermeable 4 zone or water block 17 within the upper portion of the formation 12 prevents any short circuiting or by-passing of the injected gas downwardly along well bore 11 in the direction of production perforations 21.

One or more of the aforesaid operations may be carried out consecutively with respect to the same well bore. For example, when it is found thatr the injected gas is entering production perforations 21 in excessive amounts gas injection into formation 12 via perforations 20 may be halted and the formation again treated or fractured and a gas impermeable zone created therein in the zone of the formation adjacent perforations 21, just below these perforations. Gas injection is then resumed into the formation 12 via perforations 2i) and petroleum production resumed from an even lower portion of formation 12 via other perforations, not illustrated. Further, if desired or required, water or an aqueous solution may be injected intermittenly or continuously into Water block 17'to maintain or enlarge its dimensions and to maintain its gas impermeability.

As will be apparent to those skilled in the art many alterations, modifications and changes may be made in the practice of this invention in the light of the accompanying disclosure without departing from the spirit or scope of this invention.

I claim:

1. A method of producing petroleum via a well bore penetrating a subsurface petroleum-producing formation which comprises fracturing the upper part of said formation to create therein a substantially radial fracture extending outwardly from said well bore, injecting water into said fracture to form and maintain a substantially continuous water block therein so as to create a substantially gas impermeable zone encompassing said fracture within said formation thereby dividing said formation adjacent said well bore into'an upper portion and a lower portion, packing said well bore above and adjacent said zone and below the top of said formation thereby dividing said well bore into an upper portion and a lower portion, introducing a non-oxidizing gas under pressure via said upper portion of said well bore irito said upper portion of said formation above said gas impermeable zone, and producing petroleum via tubing extending through packing means in said well bore and into said lower portion of said well bore from said lower portion of said formation beneath said gas impermeable zone.

2. A method in accordance withrclairn 1 wherein said formation is fractured by means of an aqueous liquid whereby said formation is simultaneously fractured and the resulting fracture substantially simultaneously treated to form a water block therein.

References Cited in the le of this patent UNITED STATES PATENTS 2,368,424 Reistle Jan. 30, 1945 2,593,497 Spearow Apr. 22, 1952 2,749,988 West June 12, 1956V 2,767,792 Spearow Oct. 23, 1956 2,874,777 Tadema Feb. 24, 1959 

1. A METHOD OF PRODUCING PETROLEUM VIA A WELL BORE PENETRATING A SUBSURFAE PETROLEUM-PRODUCING FORMATION WHICH COMPRISES FRACTURING THE UPPER PART OF SAID FORMATION TO CREATE THEREIN A SUBSTANTIALLY RADIAL FRACTURE EXTENDING OUTWRDLY FROM SAID WELL BORE, INJECTING WATR INTO SAID FRACTURE TO FORM AND MAINTAIN A SUBSTANTIALLY CONTINUOUS WATER BLOCK THEREIN SO AS TO CREATE A SUBSTANTIALLY GAS IMPERMEABLE ZONE ENCOMPASSING SAID FRACTURE WITHIN SAID FORMATION THEREBY DIVIDING SAID FORMATION ADJACENT SAID WELL BORE INTO AN UPPER PORTION AND A LOER PORTION, PACKING ASAID WELL BORE ABOVE AND ADJACENT SAID ZONE AND BELOW TH ETOP OF SAID FORMATION THERBY DIVIDING SAIAD WELL BORE INTO AN UPPER PORITON AND A LOWER PORTION, INTRODUCING A NON-OXIDIZING GAS UNDER PRESSURE VIA SAID UPPER PORTION OF SAID WELL BORE INTO SAID UPPER PORTION OF SAID FORMATION ABOVE SAID GAS IMPERMEABLE ZONE, AND PRODUCING PETROLEUM VIA TUBING EXTENDING THROUGH PACKING MEANS IN SAID WELL BORE AND INTO SAID 